CN102761098B - Device and method for residual current protection - Google Patents

Abstract

The invention provides a residual current protection device. The device includes: a leakage detector, a tripping device and a control circuit for generating a driving signal to make the tripping device perform a tripping action when the leakage current is detected by the leakage detector. The device also includes an external input circuit for generating a trigger signal in response to the external input, wherein the control circuit sends the driving signal in response to the trigger signal, and the power supply of the external input circuit and the slave power supply line The power sources for taking power are electrically isolated, and the signals of the external input circuit and the control circuit are also electrically isolated. Through this double isolation of power supply and signal, the external input circuit can be completely isolated from the power supply line part. As a result, even if a component is short-circuited due to a malfunction, high voltage is not applied to the button for external input, thereby ensuring the safety of the operator.

Description

Residual current protection device and method

technical field

The invention relates to a residual current protection device, in particular to a residual current protection device with an external trigger function.

Background technique

In the low-voltage power grid, when the operator touches the live part of the electrical device, a leakage current will be generated, which may easily cause personal electric shock casualty accidents. Or, when the insulation of electrical devices in the low-voltage power grid is poor, there will also be a leakage current between the live wire and the neutral wire, which may easily cause a short circuit in the line, and then cause a fire. When the above two situations occur, the power supply needs to be cut off to ensure safety.

In the low-voltage power grid, installing equipment with leakage protection function is an effective protective measure to prevent personal electric shock casualties, electrical fires and electrical equipment damage. This kind of equipment is generally called residual current protection device (Residual Current Device, RCD). The RCD detects whether there is a leakage current in the low-voltage grid. Once the RCD detects a leakage current on the power supply line, it causes the tripping mechanism in the RCD to perform a trip action, which in turn causes the circuit breaker on the power supply line to cut off the line.

In practical applications, in addition to the conventional leakage protection mentioned above, the RCD also needs to provide an external trigger function. That is to say, the RCD provides an external input terminal, and the operator can use the external input terminal to manually trigger the RCD to perform the tripping action when necessary, regardless of whether there is a leakage condition, and thereby manually disconnect the power supply line. For example, in the event of an accidental electrical device failure, the operator can manually trigger the RCD to disconnect the power supply line immediately before any leakage has occurred in order to avoid further danger. In addition, this external triggering feature allows the user to remotely test the trip mechanism and circuit breaker for proper operation.

This external triggering function of RCD is generally implemented with a simple circuit. Figure 1 exemplarily gives a simplest example. As shown in FIG. 1 , the external input circuit 140 includes a resistor R0 and an external trigger button B1 connected in series between the power supply and the ground. The voltage on the resistor R0 is monitored by a control circuit MCU1 in the RCD, and other parts of the RCD are not shown. Here, the button B1 acts as a switching element, and the voltage across the resistor R0 is low when it is turned off. When the button B1 is pressed, the switch is closed and the series branch where it is located is turned on, so the voltage on the resistor is high, which forms an effective external trigger signal. At this time, the RCD prompts the tripping mechanism therein to perform a tripping action in response to the valid external trigger signal.

In the design shown in Figure 1, the external input circuit takes power directly from the power supply line. A potential danger of such a design is that if the components that provide power to the external input circuit fail, such as being broken down, the large current on the power supply line will be directly added to the trigger button B1. If the user touches such a charged button, an electric shock accident will occur.

Therefore, the existing RCD with an external trigger function cannot meet the safety requirements, and a new type of RCD with an external trigger function is needed to avoid unnecessary personal electric shock injuries.

Contents of the invention

The invention aims to provide a residual current protection device with an external trigger function. This residual current protection device can be safely and forcibly triggered from the outside regardless of whether there is a leakage current, without causing any electric shock injury to the protection operator.

In order to achieve the above object, the residual current protection device proposed by the present invention includes: a leakage detector for detecting the leakage current on the power supply line; a control circuit for sending a driving signal when the leakage detector detects the leakage current; a tripping device for performing a tripping action in response to the driving signal; an external input circuit for generating a trigger signal in response to an external input, wherein the control circuit sends out the driving signal in response to the trigger signal, and The power supply of the external input circuit is electrically isolated from the power supply that takes power from the power supply line, and the signal of the external input circuit is also electrically isolated from the control circuit. This double isolation of power supply and signal can effectively prevent the large current on the power supply line from being directly applied to the trigger button of the external input circuit, thus ensuring the safety of the operator.

In a preferred embodiment, the electrical isolation between the power sources can use an isolation transformer, an isolated AC-DC conversion module, an isolated DC-DC conversion module, or a combination of isolated AC-DC and DC-DC conversion modules accomplish. Electrical isolation between the signals can be achieved using isolation transformers, relays, optocouplers, or magnetic couplers.

In another preferred embodiment, the power supply of the external input circuit is derived from and electrically isolated from the power supply of the control circuit. In this way, since the power of the external input circuit can be obtained from the low-voltage power supply of the control circuit, it is unnecessary to separately design filtering, voltage dividing, and voltage stabilizing circuits for the external circuit, and only need to realize the isolated DC-DC conversion. Therefore, this method is especially suitable for equipment with low cost requirements.

In yet another preferred embodiment, the power supply of the external input circuit provides power only when an enabling signal sent by the control circuit is valid. That is, when the enable signal signal is invalid, the power supply of the external input circuit is also invalid, which can further prevent the user from getting an electric shock.

In addition, according to another aspect of the present invention, the present invention also proposes a residual current protection method with external input control. The method includes: detecting the leakage current on the power supply line; sending a driving signal to drive a tripping device to perform a tripping action when the leakage current is detected; generating a trigger signal in response to an external input; and responding to the trigger signal. sending out the drive signal regardless of whether a leakage current is detected, wherein the power source for generating the trigger signal is electrically isolated from a power source that takes power from the power supply line, and the trigger signal is electrically isolated passed to the circuitry used to generate the drive signal.

Description of drawings

The following drawings are only intended to illustrate and explain the present invention schematically, and do not limit the scope of the present invention. in,

Fig. 1 shows a schematic diagram of an existing simple RCD with an external trigger function;

Fig. 2 shows a schematic diagram of a relatively complex RCD with an external trigger function in the prior art;

Fig. 3 exemplarily shows a schematic diagram of an RCD with an external trigger function according to an embodiment of the present invention;

Fig. 4 exemplarily shows a schematic diagram of an RCD with an external trigger function according to another embodiment of the present invention;

Fig. 5 exemplarily shows a schematic diagram of an RCD with an external trigger function according to yet another embodiment of the present invention.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation manners of the present invention will now be described with reference to the accompanying drawings.

Fig. 2 shows a schematic diagram of an existing RCD with an external trigger function. As shown in Figure 2, the RCD 200 includes a leakage detector 210 (for example, a zero sequence current transformer ZCT (Zero order current transformer), a control circuit 220 (such as a microcontroller MCU, or such as a control chip produced by Mitsubishi, etc.), The trip device 230 includes a trip coil 231 and a thyristor 235 , and an external input circuit 240 .

In FIG. 2 , the leakage detector 210 detects whether there is a leakage current on the live line L and the neutral line N in the circuit. The leakage current detector 210 sends the detected leakage current signal to the control circuit 220 (pins 1 and 2 ) for judgment. If the control circuit 220 determines that there is a leakage phenomenon, the pin 7 of the control circuit 220 outputs a driving signal to the thyristor 235 . The thyristor 235 is turned on in response to the driving signal, thereby prompting the tripping coil 231 to perform a tripping action due to a sudden large current.

In the RCD 200 shown in FIG. 2, the external input circuit 240 provides an external trigger signal Vt to the control circuit 220, so that the control circuit sends out the action of driving the tripping coil from the pin 7 regardless of whether there is a leakage phenomenon. drive signal. Specifically, as shown in FIG. 2 , the power supply part 241 of the external input circuit 240 is powered by the line voltage V after rectification and filtering. The power supply part 241 includes a MOS field effect transistor M1, a Zener diode D5 and a large resistor R1 (such as 1000KΩ) connected in series. When M1 is turned on, a stable voltage Va can be obtained on the cathode of Zener diode D5 (point A). The voltage Va is applied to the input section 243 of the external input circuit 240 as a power source. As shown in FIG. 2 , the input portion 243 is a series branch including two resistors R2 and R3 and an external trigger button 245 . The voltage Vt on the resistor R3 is monitored by the pin 6 of the control circuit 220 . When the external trigger button 245 is off, Vt is low. On the contrary, when the external trigger button 245 is pressed, the input part 243 is turned on, and the voltage Vt on R3 is high. Once the control circuit 220 detects that Vt is high, it immediately sends a driving signal from the pin 7, thereby prompting the thyristor to conduct and the tripping coil to trip.

In the external input circuit 240 shown in FIG. 2 , an external input enabling circuit is also preferably designed. As shown, pin 5 of the control circuit 220 is connected to the gate of M1. In this way, only when the pin 5 of the control circuit 220 outputs an effective enable signal, that is, a high level, M1 is turned on, and the external input circuit 240 is powered on, otherwise the external input is invalid.

It can be seen from FIG. 2 that the power supply part of the external input circuit 240 is directly powered from the power supply line L. As shown in FIG. In this case, if M1 fails, such as being broken down, M1 is equivalent to being short-circuited (as shown by line L1 in FIG. 2 ). At this time, the high voltage (high current) on the power supply line will be directly added to the input part 243 (as shown by the middle line L2 in FIG. 1 ), so that the person who touches the trigger button 245 will be easily injured or killed by electric shock.

In order to avoid the danger of the circuit shown in Figure 2, the present invention proposes a new type of RCD with an external trigger function. Fig. 3 schematically shows a schematic diagram of an RCD 300 according to the present invention. The RCD 300 shown in FIG. 3 is the same as that of FIG. 2 except for the external input circuit 340, so the same components and circuits are not repeated for brevity. However, those skilled in the art should understand that other parts of the RCD proposed by the present invention, except for the external input circuit 340, may also have other structures different from those shown in FIG. Drive other mechanisms such as trip coils.

Different from FIG. 2, the power supply part 341 of the external input circuit 340 in FIG. 3 no longer takes power directly from the power supply line, but from a certain power supply in the RCD in an electrically isolated manner (such as a power supply that is powered from the power supply line) Get electricity. Meanwhile, the input part 343 is also connected to the control circuit 220 in a signal isolation manner (344). Through this double isolation of power supply and signal, the external input circuit 340 can be completely isolated from the power supply line. Thus, even if elements in the RCD shown in FIG. 3 are short-circuited due to failure, high voltage is not applied to the external input button 245, thereby ensuring the safety of the operator.

The isolation of the power supply and the isolation of the signal shown in Fig. 3 can be realized in various ways. For example, power isolation can be implemented by using an isolation transformer, or by using an isolated AC-DC conversion module, DC-DC conversion module, or a combination of AC-DC and DC-DC conversion modules. Similarly, signal isolation can also be achieved by devices such as isolation transformers, relays, optocouplers, or magnetic couplers. Figure 4 and Figure 5 respectively show two specific examples of external input circuits.

FIG. 4 shows an example of an RCD 400 with an external trigger function according to one embodiment of the present invention. In FIG. 4, the external input circuit 440 of the RCD 400 includes a power supply part 441, an input part 443, and an optocoupler 444 as a signal isolation device. The power supply part 441 is an isolation transformer T1, the primary stage of which is connected to the rectified power supply line voltage, and the secondary stage is further rectified to provide a stable low voltage, such as 5V, for the input part 443 . The primary stage and the secondary stage in the isolation transformer T1 are electrically isolated, in other words, the primary stage and the secondary stage are electrically isolated. Accordingly, the current from the power supply line on the primary side of T1 does not flow to the external input circuit portion. In addition, an optocoupler 444 is used in the external input circuit shown in FIG. 4 to realize signal isolation between the input part 443 and the control circuit 220 . If the trigger button 245 is closed, the branch of the input part is turned on, and the electro-optic diode in the optocoupler 444 is powered to emit light, that is, the electrical signal is converted into an optical signal. The optical signal excites the phototransistor in the optocoupler to turn on, thereby pulling the level of the monitoring pin 6 of the control circuit 220 from high to low. After the control circuit 220 detects the active-low trigger signal, it generates a driving signal, so that the tripping device performs a tripping action. Electrical isolation is realized between the control circuit 220 and the external input circuit 440 through an optocoupler. Therefore, even if other parts of the RCD have a large current due to component failure, this large current will not flow to the button 245 through the signal path, thereby preventing the operator from being shocked.

FIG. 5 shows an example of an RCD 500 with an external trigger function according to another embodiment of the present invention. In FIG. 5 , the power supply part 541 of the external input circuit 540 obtains power from the DC power supply Vcc (5V) of the control circuit 220 through an isolated DC-DC converter. The DC power supply Vcc may be a rectified low-voltage power supply originally used to supply power to the control circuit. Here, the isolated DC-DC converter may be, for example, an AduM600 converter provided by Analog Devices, or other similar isolated DC-DC converters. In addition, a relay 544 is used as a signal isolation device between the input part 543 and the control circuit 220 in FIG. 5 . As shown in FIG. 5 , if the trigger button 245 is closed, the branch of the input part is turned on, and the relay 544 is energized to make the switch K1 turn on. Therefore, the control circuit 220 sends a driving signal to trigger the tripping device to perform a tripping operation because its pin 6 obtains a high level.

Preferably, in the example shown in FIG. 5 , similar to FIG. 2 , the control circuit 220 can also provide an external input enable signal. The signal can be sent from the pin 5 of the control circuit 220 as shown in FIG. 2 . When the enable signal is valid (such as high level), the power supply of the external input circuit is powered. On the contrary, if the enable signal is invalid, the RCD cannot be triggered even if the user presses the external trigger button.

Those skilled in the art can understand that the power isolation device and the signal isolation device in Fig. 4 and Fig. 5 can also have various other structures. For example, the power supply part of the external input circuit can also be implemented by an isolated AC-DC converter, or by first AC-DC and then DC-DC conversion. This point is obvious to those skilled in the art. Similarly, the signal isolation device can also use a conversion device such as a magnetic coupler to achieve electrical isolation. In addition, although the input part of the external input circuit shown in FIG. 4 and FIG. 5 is basically the same, those skilled in the art can understand that the input part can also be implemented by using other circuit structures well known in the art, such as using The branch of the parallel resistor is used as the input part and so on.

As mentioned above, with the RCD as shown in Figure 3-5, since the external input circuit is isolated from other circuits of the RCD by the double isolation method of power isolation and signal isolation, even if there is a component failure in the RCD, high voltage or Large current will not be added to the external trigger button, so as to ensure that the operator is not injured by electric shock.

It should be understood that although this description is described according to various embodiments, not each embodiment only includes an independent technical solution, and this description of the description is only for clarity, and those skilled in the art should take the description as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

The above descriptions are only illustrative specific implementations of the present invention, and are not intended to limit the scope of the present invention. Any equivalent changes, modifications and combinations made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the protection scope of the present invention.

Claims (6)

1. A residual current protection device (300), comprising: A leakage detector (210), used to detect the leakage current on the power supply line; a control circuit (220), configured to send a driving signal when the leakage current is detected by the leakage detector (210); a tripping device (230), performing a tripping action in response to said drive signal from said control circuit (220); an external input circuit (340, 440, 540), for generating a trigger signal in response to an external input; Wherein, the control circuit (220) further sends out the drive signal in response to the trigger signal from the external input circuit, and The power supply of the external input circuit (340, 440, 540) is electrically isolated from the power supply that takes power from the power supply line, and the signal of the external input circuit (340, 440, 540) and the control circuit (220) are also electrically isolated. 2. The residual current protection device according to claim 1, wherein the electrical isolation between the power sources uses a combination of isolated AC-DC and DC-DC conversion modules, an isolation transformer, an isolated AC-DC conversion module, or Isolated DC-DC conversion module implementation. 3. The residual current protection device according to claim 2, wherein the power source of the external input circuit (540) is derived from and electrically isolated from the power source of the control circuit (220). 4. The residual current protection device according to any one of claims 1-3, wherein the electrical isolation between the signals is realized by using an isolation transformer, a relay, an optocoupler, or a magnetic coupler. 5. The residual current protection device according to claim 4, wherein the external input circuit (440) further comprises an optocoupler, and the trigger signal is transmitted to the control circuit (220) via the optocoupler. 6. The residual current protection device according to claim 5, wherein the power supply of the external input circuit (540) provides electric energy only when an enabling signal sent by the control circuit is valid.